176 Bulletin 235. 



unscrupulous dealers have put on the market air-slaked lime as " new- 

 process " lime. It is evident from the tests that practically as good a 

 Bordeaux mixture, both chemically and mechanically, can be made with 

 the " new-process " limes as with ordinary stone lime. But it is very es- 

 sential that the " new-process " limes be fresh or newly made. Just how 

 long these limes can stand before air-slaking I do not know, but I have 

 tested some that have stood in barrels for four or five months, and they 

 seemed to work all right. I would not recommend, however, that any of 

 the " new-process " limes be used when more than a year old. One can 

 easily make a simple test, which will soon determine whether the lime is 

 good. Take a small quantity and make up a little Bordeaux mixture 

 according to the formula given above, and use the ferro-cyanide test. 

 Five cents' worth of these poison crystals dissolved in a pint of water will 

 last a season or two for testing. If the test liquid turns a dark brown 

 color as soon as a few drops touch the Bordeaux more lime must be added 

 until the liquid does not change color. Litmus paper can be used for 

 determining when the sulfate is neutralized. If the five pounds of lime 

 considerably more than neutralizes the five pounds of copper sulfate, and 

 the mixture does not settle very fast, it would be safe to purchase such 

 lime in quantities for spraying. Another simple test for these prepared 

 limes is to take a small amount of the lime, about one-half teaspoonful, 

 drop it into a little hot vinegar, and if it effervesces or " sizzles " it con- 

 tains carbonate of lime and will probably make good Bordeaux mixture. 

 I would not buy any " new-process " limes without first making one of 

 these simple tests, because, as shown above, they will all air-slake in time. 

 The prepared limes cost a little more than stone lime per barrel, but 

 when you buy a barrel, all of the material can be used rather than one- 

 half or two-thirds of it in the center of the barrel, as in the case of stone 

 lime. Then it is much easier merely to dump the lime into water and stir 

 it up without having to wait for it and watch it while slaking. Do not 

 dump the dry lime into the copper sulfate solution, even when the 

 latter is much diluted. I have received many inquiries regarding these 

 limes, and have gained much information from the experiments described 

 above. I hope the facts have been put in such a way that, by the aid of 

 the illustrations, farmers will be able to get a better notion regarding the 

 proper making of Bordeaux mixture, and that these comparative tests of 

 " new-process " limes with stone lime may benefit the public. 



